"Warnings from the Ice"

ANNOUNCER: Tonight, on NOVA, is Antarctica melting? A mountain of ice is on
the move, and its fate could spell disaster.

ROBERT BINDSCHADLER: It does matter to everybody in the world what that ice
sheet is doing.

ANNOUNCER: Are we on the verge of the next Ice Age? Or a great flood that may
consume the world's coastlines? The race for answers sparks a NOVA expedition
to the ends of the earth. "Warnings from the Ice."

Major funding for NOVA is provided by the Park Foundation. Dedicated to
education and quality television.

And by Iomega, makers of personal storage solutions for your computer, so you
can create more, share more, save more and do more of whatever it is you do.
Iomega. Because it's your stuff.

This program is funded in part by Northwestern Mutual Life, which has been
protecting families and businesses for generations. Have you heard from the
Quiet Company? Northwestern Mutual Life.

The Corporation for Public Broadcasting. And viewers like you.

Additional funding for this program was provided by the Richard Saltonstall
Charitable Foundation.

NARRATOR: The bottom of the world is a beautiful, but unforgiving place. An
entire continent cloaked in ice. Antarctica. Just over 700 miles from South
America, yet it's so isolated, its existence was a myth until the 19th century.
For over 20 million years, Antarctica has been the coldest place on earth. But
recently, things have been heating up. In 1995, an iceberg the size of Rhode
Island broke off from the Larsen ice shelf along the Antarctic coast. And a
large portion of the ice shelf disintegrated in a matter of days. Over the
last half century, the coastal ice on the Antarctic Peninsula has been
gradually disappearing. What does it mean? Is Antarctica melting? What would
happen if all this ice were unleashed into the oceans? Kevin Costner's epic
film, "Waterworld," depicts Hollywood's version of the disaster: a future
where dry earth is rare and precious. Beneath the waves, civilization lies
destroyed, drowned by melted polar ice caps. Is this a science fiction
fantasy? Or could "Waterworld" really happen? To find out, scientists are
heading south, to Antarctica. Their first stop is New Zealand, where they gear
up to battle the elements. Then, it's an eight-hour flight in a military cargo
plane. The LC-130 Hercules, affectionately know as the "Herc," is not designed
for comfort. But it's one of the few planes tough enough to do the job. Every
summer, Hercs deliver hundreds of scientists to Antarctica. They have just a
few short weeks to unload supplies, set up camp, and collect crucial data
before the dark polar winter sets in. These are the ice experts. They're on a
mission to unlock the secrets of Antarctic ice. Is it melting? Is it moving?
Most importantly, how will it affect the rest of the world? Taking the pulse
of Antarctica is a daunting task. The continent is one and a half times the
size of the U.S., and is covered with seven million cubic miles of ice. The
giant ice sheet in the east is probably more than 15 million years old. But
the West Antarctic Ice Sheet is younger, and scientists fear, much less stable.
While the ice on the eastern side of the continent rests on dry land, most of
the West Antarctic Ice Sheet sits precariously on bedrock that lies below sea
level. Part of the ice sheet is in direct contact with sea water, which is
much warmer than the air. And that means the ice can melt much faster. The
West Antarctic Ice Sheet is as big as Mexico. If it broke up and fell into the
ocean, sea level would rise by almost 20 feet. That's enough to redraw the
world's coastlines, flooding Bangladesh, and Florida, London and New Orleans.
The deluge would wipe out entire cities, and render millions of people
homeless. Many experts believe the West Antarctic Ice Sheet is doomed to
collapse. The question is, how long will it take? Two thousand years? Or a
few decades? The answer may lie in the nature of the ice itself. The ice
sheet is made up of layers of snow that piled higher and higher over the
millennia, and then compacted, under their own weight, into ice. In some
areas, the ice sheet is almost three miles deep. And when ice gets this thick,
it can't sit still. Antarctic ice is constantly on the move. When the ice
sheet reaches the mountains, it squeezes through the ridges, forming valley
glaciers. Across the continent, scientists are trying to track the movements
of the ice. On the eastern side, one research team is probing the depths of
the Meserve Glacier. A year ago, chainsaws carved this 200-foot tunnel into
the heart of the ice.

CHARLES RAYMOND: A tunnel provides one with a spatial picture that you can
look at the geometry of these features in a way that's unique. You can't do it
any other way.

NARRATOR: Charles Raymond is trying to understand ice moves.

CHARLES RAYMOND: We put these bolts in vertical lines about a year ago. And
we've lined those lines up so that these figures were actually squares. And
what's happened in the meantime over the intervening year is that the top up
there has moved this way, and this down here has stayed relatively fixed in
place. And so, there's been this kind of motion, which we call shearing, that
deformed these lines into inclined lines, from vertical to inclined. And the
little squares are now parallelograms.

NARRATOR: The bolts reveal that the ice at the bottom of the glacier only
moved about a fifth of an inch in the last year. But the ice above it flowed
much faster. The top of the Meserve Glacier moved about six feet.

RICHARD B. ALLEY: What we have to remember first is that the ice moves. It
flows, and if you think about taking pancake batter and pouring it onto a
plate, it will spread. Gravity pulls it down, it schlumps out, and so it
flows. Ice does exactly the same thing. It snows on top of the glacier. The
weight of the ice pushes it down, and it spreads out. And so, you have moving
ice.

NARRATOR: The ice in Antarctica is so thick, gravity forces it to spread out
towards its edges. Eventually, there's only once place for the ice sheet to
go: into the sea. As it pushes off the coast, the ice thins out and begins to
float. It is now called an ice shelf. Above the water, the ice shelves look
like towering cliffs. But they are actually just the tops of enormous floating
ledges of ice, that extend hundreds of feet beneath the surface. As the
shelves break apart, colossal icebergs are launched into the southern oceans.
Antarctic icebergs are famous for their extraordinary size—often several
miles long. Floating among the majestic icebergs is a less glamorous type of
ice, but one that's extremely important for Antarctic wildlife. Sea ice forms
when ocean water freezes. Just a few feet thick, sea ice is the perfect
platform for marine mammals like seals, and for birds, especially penguins. In
the water, penguins hunt for krill, fish, and squid. But they mate and breed
on land, or on the shifting sea ice itself. During the winter, as air
temperatures drop, the sea ice freezes into sheets and expands outward from the
coasts. This image, produced by microwaves, shows how sea ice grows and
shrinks with the seasons. At the height of winter, the thin veneer of ice
stretches almost 1,000 miles across the ocean, in effect, doubling the size of
the continent. Sea ice protected Antarctica from human invasion for thousands
of years. When sailors finally did venture south, the floating ice tormented
them. In 1914, the British ship, Endurance, headed for Antarctica. Explorer
Ernest Shackleton was hoping to march across the entire continent. But he
never made it ashore. Sea ice closed in around the Endurance, and carried it
in an aimless drift for nine months. Documenting their ordeal with a film
camera, the crew struggled to cut the boat free, but failed. Finally, they
were forced to abandon ship, and could only watch helplessly as the mighty
Endurance was broken and crushed by the shifting ice. Civilization was more
than 1,000 miles away, and Shackleton was left with just three small lifeboats.
He spent nearly a year battling crushing ice floes and hurricane seas, but
overcame the odds. With one of the boats, he was able to reach a small whaling
station in the South Atlantic. Two years after they'd set out, the crew of the
Endurance was rescued. Amazingly, all 28 men survived. Antarctic exploration
has come a long way in the last 85 years. Today, 13,000-ton steel-hulled ice
breakers slice their way to the coast. One of the early camps has exploded
into a scientific boomtown. McMurdo Station is headquarters for the U.S.
Antarctic Program, supported by the National Science Foundation. Hundreds of
scientists are based here. Many of them study the crucial relationship between
ice and climate. In the last century, global temperatures have risen about one
degree Fahrenheit, possibly as a result of industrial activity. But on the
Antarctic Peninsula, it's warmed up more than four degrees during the same
period. Here, large chunks of the floating ice shelf are breaking away. And
native plants are thriving along the rocky coast. Scientists do not blame
global warming for the massive meltdown. Instead, they believe it's part of a
natural local climate shift. Looking back in time, it's clear that climate has
undergone some major changes, with direct impact on the size of the ice sheets.

RICHARD B. ALLEY: In the last million years, the glaciers have grown and
shrunk about 10 times. And they typically spend about 90,000 years growing and
10,000 years melting, and 90,000 years growing and 10,00 years melting, and so
on.

NARRATOR: Ice Ages, each lasting 100,000 years, have come and gone, again and
again. At the height of the last Ice Age, 21,000 years ago, much of North
America was frozen under a giant ice sheet, and temperatures were about 20
degrees colder than they are now. Today, we are in one of the shorter, warm
periods between the Ice Ages, called interglacials, when much of the ice melts.
As it melts, more and more water flows into the oceans, and sea level goes up.

RICHARD B. ALLEY: Sea level is ultimately controlled by how much water is in
the ocean and by how hot that water is. If we take water out of the ocean and
put it in an ice sheet, then the ocean gets lower. If we take water out of the
ice sheet and put it back in the ocean, sea level comes up.

NARRATOR: During the Ice Ages, water accumulated in the expanding ice sheets,
and global sea level went down. But for the last 20,000 years, the ice has
been melting, and the oceans are getting bigger.

ROBERT BINDSCHADLER: Over the last 20,000 years, sea level has been rising.
Over the last 4,000 years, it's been rising at about two millimeters a year.
And so, the concern is whether that rate is going to continue or whether it's
going to accelerate or whether it might even decelerate.

NARRATOR: So far, the collapsing ice shelves haven't raised sea level at all,
because they were already floating, and displacing water, long before they
broke up. For sea level to rise significantly, ice from a grounded ice sheet
has to flow rapidly into the sea. And that's most likely to happen in West
Antarctica, where the ice sits on bedrock below sea level. To find out how
vulnerable this ice sheet is, scientists like Bob Bindschadler are heading out
into the Antarctic wilderness.

ROBERT BINDSCHADLER: We're out there trying to understand how the ice sheet
works. What are the forces that make the ice move? And if those forces
change, how is the ice sheet going to respond to those changes?

NARRATOR: But tracking the West Antarctic ice sheet isn't easy. Even during
the summer months, conditions can be brutal. The team's only protection is an
insulated box that serves as a travelling base camp. It's a kitchen, lab, and
dormitory squeezed into a 10-foot by 10-foot room. When the winds die down,
team members set out in pairs across the surface of the ice. Their mission is
to locate and map hundreds of marker poles spread out across 4,000 square miles
of the West Antarctic Ice Sheet.

ROBERT BINDSCHADLER: We use global positioning satellite receivers which tell
us our precise location. So, we go to a site and we put the receiver antenna
on top of the pole, measure its position, and then come back a year late and
re-measure its position, and then, that tells us how far it's moved in that
year.

NARRATOR: Pole by pole and day after day, the team collects the data. Every
few days, base camp moves on, and the process repeats itself—until something
breaks down. With the windchill plunging to 50 below, equipment repair is a
challenge.

ROBERT BINDSCHADLER: Fixing the skidoo in the cold is really difficult. One
of the problems is that your tools have been outside, probably. So, they're
very cold, so you're not going to be able to work with bare hands, fingers.
So, trying to put a socket on a nut can be difficult. Maneuvering some of the
tools in tight spaces can be difficult. And you'll drop things and it will go
into the snow and you won't be able to find it, and you'll just be fishing
around for half an hour just trying to find the nut that just fell. So, those
kinds of frustrations just limit your ability to move and do the things that
you're accustomed to being able to do.

NARRATOR: As they make their daily rounds, the scientists face more than
frustration and cold. The movement of the ice sheet can open up gaping cracks,
called crevasses. Crevasses can be 50 feet wide and more than 100 feet deep.
Worst of all, sometimes they're invisible, covered by fragile bridges formed by
blowing snow. Walking along the surface, a researcher would never see the
giant chasms—until it's too late. This was a demonstration, but Bob
Bindschadler knows firsthand the terror of an unexpected plunge.

ROBERT BINDSCHADLER: It's just like having a rug pulled out from underneath
you, that you're walking on something that you think is a firm surface and all
of a sudden, it disappears. And you just shoot downward.

NARRATOR: Bob must be all the more vigilant, because he spends much of his
time driving a heavy skidoo across the ice.

ROBERT BINDSCHADLER: The skidoo makes it even more hazardous, because you have
something that is about five times your weight, and if the two of you fall into
a hole, you don't want to be anywhere close to that machine.

NARRATOR: Over the years, crevasses have killed several explorers and
scientists. In this case, the driver survived. But his bulldozer is lost
forever. The data that Bob's team is collecting may help to explain why parts
of the ice sheet are riddled with crevasses. Measurements reveal that some of
the poles have moved almost half a mile in a single year. They are riding on a
200-mile long ribbon of rapidly flowing ice, called an ice stream.

ROBERT BINDSCHADLER: The ice stream is probably best described as just a river
of ice contained within the ice sheet. Ice sheets in general are thought to be
very slow moving features, slow moving just meaning just a few feet per year.
But these ice streams, these faster rivers, rapid currents, will go about a few
hundred meters per year, up to 700 meters per year, in the case of the ice
streams that we're studying.

NARRATOR: The ice streams move so fast, friction at the sides splits open the
ice, creating enormous crevasse fields. The ice streams are so large, their
true size and shape can only be appreciated from space. Satellite imagery of
West Antarctica reveals several areas where rapid movement has occurred.
Through these ice streams, highlighted in blue, ice is flowing from the heart
of the West Antarctic Ice Sheet out into the huge, floating Ross Ice Shelf.

DONALD BLANKENSHIP: Ice streams are 50 to 100 kilometers wide, about a
kilometer thick. They go 10 to 100 times faster than the interior ice. So,
they're capable of moving vast amounts of material into the oceans.

NARRATOR: But why are the ice streams moving so fast? Geologist Don
Blankenship believes the answers lie beneath the ice, in the rocks that support
it.

DONALD BLANKENSHIP: The problem of understanding the dynamics of the West
Antarctic Ice Sheet in the context of the geology is that the geology is
largely unknown. It's covered with ice. If something sticks up through the
ice to study, to get a piece of, to get a rock, it's probably an anomaly. It's
not telling us what's really going on. What's really going on is a secret.

NARRATOR: To see the rocks beneath the ice, Don Blankenship would need x-ray
vision. Thanks to this airplane, he has it. This Twin Otter is scanning the
ice sheet with a slew of hi-tech remote sensors, including radar that can see
right through the ice.

DONALD BLANKENSHIP: The ice-penetrating radar gives us the bed. The laser
altimeter gives us the nuances of the surface to within a fraction of a meter.

NARRATOR: And there are instruments that measure the magnetism of the rocks,
as well as the gravitational pull of the earth.

DONALD BLANKENSHIP: With the aircraft, we can fly around and get at least
indirect indications of where the rocks are dense, where the volcanic rocks
are, where vaults are—all kinds of things that we can put together to
understand the geology.

NARRATOR: Flying over the ice sheet, the sensors detected rocks that were less
dense, a characteristic of sedimentary layers, which form at the bottom of
oceans. In another experiment, sound waves revealed evidence of a layer of
soft, wet mud, directly below the ice streams. Don believed that this mud was
making the ice streams flow so fast. But to prove this idea would take a more
direct approach.

BARCLAY KAMB: Our approach is to get access to the base, where the action is—where we believe the action is. And we do that by drilling.

NARRATOR: Barclay Kamb is part of a team that's drilling a hole straight down
through an ice stream to take samples from the bed below. If there's mud down
there, he's going to find it.

BARCLAY KAMB: The normal methods of drilling—It takes a year or so to drill
a hole deep enough to serve the purpose. To get an appreciable amount of
information, we have to do it much faster than that. So, we have a hot water
jet that melts its way rapidly down into the ice.

NARRATOR: Finding water to supply the jet was no problem. But producing and
maintaining enough heat was a bigger challenge. To do the job, the team
converted eight carwash heaters into industrial-strength ice melters.

BARCLAY KAMB: The temperature of the ice is minus 25 degrees centigrade, and
the air temperature is always below freezing.

NARRATOR: The near boiling water is pumped through almost a mile of rubber
hose and pressurized to 1,500 pounds per square inch. The resulting jet easily
cuts through the rock-hard ice.

BARCLAY KAMB: The biggest single challenge of the cold to our operation is the
hazard that some part of this system will freeze up, or all of it will freeze
up.

NARRATOR: To avoid freezing, the drill must operate continuously until it
reaches the bottom, more than half a mile down.

BARCLAY KAMB: We can drill a hole roughly 3,000 feed deep within a time less
than a day. And then, we can get to the bottom, and then put down instruments
that will reveal something about what goes on there.

NARRATOR: Just as Don Blankenship had predicted, the team found mud directly
under the ice stream. When they pulled up their probe, it was coated with a
thick, gooey mixture of wet clay, sand, and pebbles. Under the microscope,
they found these diatoms, the tiny fossils of prehistoric algae. Together, the
evidence points to one conclusion. Where there is now an ice sheet, there once
was an ocean.

DONALD BLANKENSHIP: One thing we all agree on is the West Antarctic Ice Sheet
does disappear during the interglacial periods which happen about every 100,000
years. It may not disappear in this one, the current one that we're in, but it
does disappear. The question that's really important is, what triggers the
disappearance?

NARRATOR: The ice streams are key to solving the puzzle. By carrying large
amounts of ice quickly into the sea, they are gradually eating away at the ice
sheet. But what's driving the ice streams forward? Is it just the underlying
mud? Barclay Kamb's drill turned up some intriguing evidence that something
else might be going on. A half a mile down, he found signs of a very thin
layer of water, possibly less than a millimeter thick, flowing between the mud
and the ice.

BARCLAY KAMB: We learned there that the base of the ice is at the melting
point. And we learned that that pressure of water at the base of the ice is
very high. It's almost high enough to float the glacier off its bed, and that
is a physical driving phenomenon which allows a rapid motion, this near
flotation of the ice.

NARRATOR: But where is the water coming from? Why is the base of the ice
melting? While flying over the ice sheet, Don Blankenship's sensors picked up
evidence of magnetic rock, and a cone-shaped mountain beneath the ice. At the
surface, there was a round depression—four miles wide.

DONALD BLANKENSHIP: Ice flows downhill, and whenever you have a depression,
that means that ice on one side is flowing and ice on the other side is flowing
in, and it has to go someplace. Mass is conserved. And so, what turns out
that the only way for that mass to go someplace is to be melting away at the
bottom for that ice to be flowing into essentially a depression on the bottom
as formed by very high heat flow.

NARRATOR: It was an active volcano, melting the bottom of the ice. Even a
volcano isn't enough to destroy an entire ice sheet, but it is evidence of some
major geological activity. Don made his discovery just west of the
Transantarctic Mountains. Here, two continental plates have moved apart. In
the middle, the earth's crust is very thin, allowing heat to flow up from
below. This could be contributing water to the base of the ice streams. But
scientists worry there could be an additional source of heat.

RICHARD B. ALLEY: We have these fast-moving ice streams, which are lubricated
on the bed, and between them are ridges of slow-moving ice which are probably
frozen to their beds. The temperature of the bed depends on a number of
things. It depends on how hot the earth is underneath and how much heat comes
up, but it also depends on how hot the atmosphere is.

NARRATOR: The atmosphere above the ice sheet is extremely cold. But during
the last Ice Age, it was even colder.

RICHARD B. ALLEY: The bed doesn't notice immediately when the temperature at
the surface changes, in the same way that, if you take the Thanksgiving turkey
out of the freezer and put it in the oven, the center of the turkey takes a
while to notice that it's in the oven. It remains frozen for a while. When
the air warmed at the end of the last Ice Age, the bed of the glacier is just
now realizing that. It takes that long for the heat to get down. So, there is
some concern that the warming at the end of the last Ice Age would now be
causing melting at the bottom, and that as more melts, it goes faster. That
makes friction, which makes heat, which melts more, which goes faster. And the
same thing—disaster.

NARRATOR: If the ice streams are speeding up, disaster could come sooner
rather than later. But it's hard for scientists to identify any long-term
trends, when they've been tracking the icy rivers for such a short time. To
forecast the future of the ice sheet, they'll need a better picture of the
past. Kendrick Taylor is one of the detectives trying to decipher the climate
history of Antarctica. He's looking for clues embedded in the ice itself.

KENDRICK TAYLOR: When I look out here, across this surface here, I see, of
course, a small portion of the West Antarctic ice sheet. This is sort of just
a small, little, teeny portion of it. But I know that underneath there,
there's just this series of layers, stacked up one on top of each other, and
those layers contain a record of what the climate has been in the past.

NARRATOR: The layers are obvious just beneath the surface.

KENDRICK TAYLOR: This is the surface of the snow, right up here. This is a
winter sequence, the darker snow up here. That's snow that fell last winter.
This very light layer, it's the surface hoarfrost layer, which formed last
summer when it was warm out. This is a dense layer here, another winter
sequencing here. And then, this is a summer sequence right in here. And
what's really interesting about this is, just by looking at this, I can tell
you certain things about what the weather used to be like here. Firstoff, this
winter, it snowed a lot more than this winter did. You can tell that simply
because it's thicker. And during the summer, this summer was particularly
warm. You can tell that because of this ice layer right in there. That
happens when the snow gets very warm. It gets kind of slushy, and that surface
layer re-freezes and forms a very hard ice crust. What's going to happen here
is, more snow is going to fall on the surface, and this whole sequence here is
going to get compacted and compacted down until it becomes solid ice.

NARRATOR: Ken's job is to retrieve the compacted layers in an ice core. Each
meter-long cylinder of ice represents about 10 to 20 years of snowfall.

KENDRICK TAYLOR: This ice core is going to give us a window on what has
happened in the past. By looking at this ice, we're going to be able to pull
up ice that's over 100,000 years old. We can make measurements on that ice,
and we can determine what the climate has been for 100,000 years, and we can
determine the general nature of this ice sheet during that 100,000 year period.
So, for some of the ice cores, we have to be very careful about how we collect
them. We have to wear special suits and handle them very carefully to make
sure that we don't contaminate the core in a process of working with them.

NARRATOR: Scientists have been collecting ice cores for decades, but small
rigs, like this one, can only drill about 450 feet. The ice at that level is
only about 1,800 years old. At this site, the really old ice is more than a
half-mile down. Reaching those depths requires a very long drill. This is the
biggest ice core drill rig in the world. Ken's team will use it to drill
through Siple Dome, a ridge of ice that rises up between two ice streams. The
ice core they collect will provide important clues about the history of the
West Antarctic Ice Sheet. That is, if they can get the drill to work. Gregg
Lamorey is one of the managers on the project.

GREGG LAMOREY: We broke one of the couplings that connects that shaft to the
inner core barrel that does the actual drilling. They don't have this
particular coupling in McMurdo. They are able to machine it up for us in a
couple of hours, because it's not a very hard part to make. They have a very
good machine shop there. But now, we're really waiting on the weather, and
around here, the weather can sock you in for over a week sometimes. And they
just can't get the Herc flights in. And so, until we can get that part in off
the Herc, we're kind of held up.

NARRATOR: For the crew at Siple Dome, sitting out a summer blizzard is
frustrating, but not life-threatening. More than 50 people live here at one
time, and they have shelter, heat, and food to weather the storm. But this
wasn't always the case. Frozen in time by the dry, Antarctic air, the supply
hut of Robert Falcon Scott has sat undisturbed for almost a century. A British
Naval Officer, Scott led two high-profile expeditions to the frozen continent.
In 1911, he set out for the Holy Grail of Antarctic exploration: the South
Pole. The journey would take him across almost 1,000 miles of icy terrain,
deep into the heart of the continent. He rejected the use of sled dogs to haul
provisions, instead relying on Manchurian ponies. They were soon hobbled by
the extreme cold, and Scott and his four companions were left to drag their
supplies on foot. After 10 weeks of exhausting labor, they arrived at the
Pole, where they found an empty tent. A Norwegian team had beaten them by one
month. Scott recorded his feelings in a diary.

VOICE OF ROBERT SCOTT: It is a terrible disappointment, and I'm very sorry for
my loyal companions. It will be a wearisome return. Great God! This is an
awful place.

NARRATOR: Malnourished and depressed, the British headed for home. But they
never made it. A relentless wind storm stopped Scott in his tracks, just 11
miles from a supply depot.

VOICE OF ROBERT SCOTT: We shall stick it out to the end. But we are getting
weaker, of course. It seems a pity, but I do not think I can write more.

NARRATOR: Eight months later, rescuers found Scott and his companions, frozen
in their sleeping bags. They covered the site with a monument of snow, and
Scott's tent became his grave. Today, visitors are better prepared for the
unforgiving Antarctic weather.

STEVE DUNBAR: When we're out here in Antarctica, it can be relatively benign
weather sometimes, and then sometimes it can change pretty violently for the
worse in a relatively short period of time.

NARRATOR: Steve Dunbar teaches scientists how to survive the worst Antarctica
has to offer—including winds that can reach 100 miles an hour, and winter
temperatures that plunge to more than 70 below zero.

STEVE DUNBAR: I was out here one time doing a search and rescue exercise with
some people, and the weather ended up closing in. And I watched it. From
about three miles away, there's a good landmark, and I watched it come in, and
in less than two minutes, we had less than 20-foot visibility. You darn well
better get a camp up and get out of the elements or you're not going to last
very long out in this sort of weather. The shelter is probably the most
important things that you need to do, and you need to get that up first.

NARRATOR: Most scientists come in the summer, but even then, they face the
treat of sudden storms.

STEVE DUNBAR: Calories are gold, and all the calories that you have on board,
all that food that you've eaten, and all the fats that you have stored, you
only have so many of them. And when you run into a situation here where you
find yourself stressed by the weather or stressed by the environment, you need
to go ahead and hang onto all those calories and spend them wisely. So, you
want to go ahead and build your snow shelter as quickly and as efficiently as
possible.

NARRATOR: Stronger than any tent, the best protection from the biting winds is
a shelter made from blocks of snow.

STEVE DUNBAR: It's really dramatic. The second you get in your shelter, you
just feel that much warmer.

NARRATOR: Safety is always an issue in Antarctica, especially in the isolated
research camps like Siple Dome, where Ken Taylor's team has been waiting
patiently for a replacement part for the big drill. Finally, the weather has
cleared, and the new coupling is flown in from McMurdo, almost 600 miles away.
With time running out on their work season, the crew has only drilled about 25
feet, with 3,000 more to go. In all, it will take three or four summers to
reach the bottom. The drillers are weathered veterans of ice sheet research.
Before coming to Antarctica, many of them investigated the ice on the opposite
side of the planet—in Greenland. Like Antarctica, much of Greenland is
covered with an enormous ice cap, the last of the great northern ice sheets.
The ice is over two miles deep, and the bottom is made from snow that fell
about 250,000 years ago. American and European teams collected ice cores here
that have revolutionized our vision of climate. The ice cores were sliced up,
and every aspect was scrutinized in detail, from their crystalline structure to
chemical content and electrical conductivity. In this test, two electrodes are
dragged across a clean surface of the ice core. The read-out reveals
fluctuations in atmospheric dust content. A dip on the graph indicates more
dust, and a drier, colder climate. Climate experts used to believe that the
warm-up after the last Ice Age was slow and steady. But the Greenland ice
cores told a very different story. Instead of gradual warming, occurring over
thousands of years, the end of the Ice Age, 11,000 years ago came suddenly and
swiftly.

RICHARD B. ALLEY: When you look at the long record, the warm-up from the Ice
Age to today was not a smooth process. It jumped. It would be coming along
and then—Boing!—the world changed. And the "boing" may have taken 50
years, it may have taken 20 years, some of the "boings" one to three years.
And the change is something, a third to a half of the whole warming from the
Ice Age. Just, the world changed.

NARRATOR: Looking back in time, the last 10,000 years have been marked by
dramatic changes, century-long cold spells and decades of drought. But these
were nothing compared to what came before, when average yearly temperatures
fluctuated widely, creating climate shifts within a human lifetime that are
nearly unimaginable.

RICHARD B. ALLEY: If we remember the Dust Bowl, it got dry and the fields blew
away and the crops died and people starved or they moved. The Dust Bowl was a
change in the weather, a change in the climate that would be barely a blip in
the climate records we're seeing. So, if you think of the impact of the Dust
Bowl on the people living in Oklahoma when that happened, that was a small
change. That was not a big change.

NARRATOR: This is the crucial distinction between climate and weather. The
natural disasters we've known, including hurricanes, tornadoes, and floods, are
weather events, taking place in a climate that is basically stable and
predictable. But if the climate changed, if the average temperature suddenly
went up or down by even a few degrees, it could radically disrupt life as we
know it.

KENDRICK TAYLOR: One way to think of these large changes in climates is, it's
as if the climate that you find up in the midwest, in Iowa or something like
that, was suddenly occurring down in Texas.

NARRATOR: The cause of such rapid shifts is a mystery. But some scientists
fear there are critical thresholds in our climate, that once crossed, could
trigger the sudden change.

KENDRICK TAYLOR: What is means is that there may be sort of triggers or
thresholds in the climate system, so that you can be in this one climate state
and you can be changing something—perhaps greenhouse gases, perhaps other
aspects of the climate system—and you won't see any other change, or very
much change in climate. And then, once you cross a critical threshold, or you
sort of trip a trigger, if you will, the climate abruptly changes to another
state. And it catches you by surprise. So, you can be sort of monitoring
climate and you can be saying, "Well, there's nothing going on, and there's no
real changes. We don't have anything to worry about." And then, all of a
sudden—Boom!—you've got a problem. And it's there. And it's sort of too
late to do anything about it.

NARRATOR: When it comes to global warming, popular fears usually focus on the
Waterworld disaster, melting polar ice caps and devastating floods. But now,
there's concern that if the world gets too warm, high temperatures could help
trip a climate trigger, and plunge us into a colder and icier age. If the ice
teaches us anything, it's that there is no room for complacency. This is a
volatile world. If climate shifted abruptly in the past, not just once, but
repeatedly, it's inevitable it will happen again. The question is, when?

RICHARD B. ALLEY: Ultimately, we would like to know what faces us in the
future. Will the climate do this again? Should we get ready for it? Will our
actions effect it? If we humans do this, will the climate change? Can we
change it so that it's nice to us, or might we change it so it's very bad for
us?

NARRATOR: The ice core at Siple Dome is one piece in a giant puzzle. If
researchers can date the ice at the bottom, they may find out when the West
Antarctic Ice Sheet last collapsed. And the ice core itself could help solve
the mystery of rapid climate change. Slowly, the ice is surrendering its
secrets. Here in Antarctica, they're hoping it will answer some important
questions about our future, before it's too late.

ANNOUNCER: Where would your favorite stretch of coastline be if the West Sheet
melted? It wouldn't be. On NOVA's website, see for yourself what such a
catastrophe could do.

To order this show for $19.95 plus shipping and handling, call 1(800) 949-8670.
And to learn more about how science can solve the mysteries of our world, ask
about our many other NOVA videos.

ANNOUNCER: Next time on NOVA, frightening power. Lightening speed. And
amazing drive for survival. Brave a close encounter. "Crocodiles!"

NOVA is a production of WGBH Boston.

Major funding for NOVA is provided by the Park Foundation. Dedicated to
education and quality television.

This program is funded in part by Northwestern Mutual Life, which has been
protecting families and businesses for generations. Have you heard from the
Quiet Company? Northwestern Mutual Life.

And by Iomega, makers of the of the 1 and 2-gig JAZ drive, which lets you save
worlds of imagination and give birth to prehistoric creatures—all in a
four-inch square. Iomega. Because it's your stuff.

The Corporation for Public Broadcasting. And viewers like you.

Additional funding for this program was provided by the Richard Saltonstall
Charitable Foundation.